[asterisk-users] file command with alaw file

Danny Nicholas danny at debsinc.com
Thu May 20 08:34:27 CDT 2010


Sox v14.1.0 doesn't play with alaw, but AFAIK, Asterisk has this function
(this is from 1.4.30, think 1.6X has same functionality)
CLI> help file convert
Usage: file convert <file_in> <file_out>
    Convert from file_in to file_out. If an absolute path is not given, the
default Asterisk sounds directory will be used.

Example:
    file convert tt-weasels.gsm tt-weasels.ulaw

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Pham Quy
Sent: Thursday, May 20, 2010 2:50 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] file command with alaw file

Hi,

How can I convert FROM ALAW file, which generated by asterisk apps
(monitor, or record app), to format (wav or mp3) that is playable by
music player?? Can Sox do this?


I have an asterisk 1.6.2.6 on my CentOS 5.2. I record audio clip by
mixmonitor app and use file command to check the alaw output, and here
is output:

---------
983006584-20100517-125002.alaw: RIFF (little-endian) data, WAVE audio,
ITU G.711 A-law, mono 8000 Hz
---------

How could file command recognize the format as there is no header in the
output file? Or Did I probably miss something making asterisk yield
incorrect alaw files?

Please help, thanks

Quyps

On Thu, 2010-05-20 at 00:50 -0600, Steve Murphy wrote:
> Quyps--
> 
> I've noticed in general that the ulaw, alaw, gsm, slin files used and
> generated by 
> asterisk do not have headers (the RIFF stuff), and asterisk is not
> expecting them. in general they
> will louse up Asterisk's ability to play the sound. They are just raw
> data and the extension
> on the file name (.gsm, or .ulaw, etc) is the only clue to the file
> format/contents.
> 
> In general, if you need a sound file of your own making in a certain
> format, you can convert
> to most of the formats using sox in linux, but really, the best thing
> to do is record the source
> sound file in cd-quality sound WAV format, in 44 khz sampling rate, or
> higher, and then 
> use sox to convert to 8khz format. Asterisk can do some of this via
> the file convert CLI
> command, ( on the asterisk cli, type "help file convert"). You'd have
> to judge for yourself
> if "file convert tt-weasels.gsm tt-weasels.ulaw" which would convert
> the 8khz gsm format to
> 8 khz ulaw, or "sox -v 0.7 tt-weasels.44khz.wav -r 8000 -c 1 -t sw
> tt-weasels.raw;"
> "sox -r 8000 -c 1 -t sw tt-weasels.raw -t ul tt-weasels.ulaw"  which
> is the way the Asterisk
> sounds are produced from the the cd-quality sounds. They would seem a
> bit equivalent.
> 
> I wonder if just "sox -v 0.7 tt-weasels.44khz.wav -r 8000 -c 1 -t ul
> tt-weasels.ulaw" would
> sound any better... you audio engineers out there may have an opinion.
> 
> I've personally noted that not all linux distributions provide the
> same version of sox;
> some distribute sox with an absolute minimum of sound formats
> built-in. You may have 
> to go out and find all the libraries and roll your own sox.
> 
> murf
> 
> 
> 
> 
> 
> On Wed, May 19, 2010 at 10:34 PM, Pham Quy <quyps at vega.com.vn> wrote:
>         On Mon, 2010-05-17 at 17:49 +0700, Pham Quy wrote:
>         > On Mon, 2010-05-17 at 13:06 +0700, Pham Quy wrote:
>         > > hi all,
>         > >
>         > > I install Asterisk 1.6 on Centos 5.2 (kernel 2.6.18-92.el5
>         #1 SMP Tue
>         > > Jun 10 18:51:06 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux)
>         and do record
>         > > audio clip with mixmonitor() as alaw file (softphone is
>         also configured
>         > > with alaw active only). Using file command i can get the
>         following
>         > > information
>         > >
>         > > 983006584-20100517-125002.alaw: RIFF (little-endian) data,
>         WAVE audio,
>         > > ITU G.711 A-law, mono 8000 Hz
>         > >
>         > > But when i install the same system on Centos 5.5 (kernel
>         2.6.18-92.el5
>         > > #1 SMP Tue Jun 10 18:51:06 EDT 2008 x86_64 x86_64 x86_64
>         GNU/Linux) i
>         > > could get the same information with file command. File
>         command
>         > > recognized alaw file as JPEG image:
>         > >
>         > > 983006584-20100517-123825.alaw: JPEG image data
>         > >
>         > > I guess i may miss something when i setup the new on on
>         Centos 5.5, but
>         > > u dont know what it is. Anyone have idea about this?
>         > >
>         > > please help.
>         > >
>         > > Thanks in advance.
>         > > Quyps
>         >
>         > I did check content of two alaw files (using a hex editor)
>         generated
>         > from two aboves cases. For the one fromo CentOS 5.2,
>         beginning bytes
>         > look likes :
>         >
>         > RIFF1^0.WAVEfmt........ at ...@.......fact.....^0.data.^0...
>         >
>         > and the one from CentOS 5.5
>         >
>         > ......................RQVTV........XEMBAX............
>         >
>         > It seem like the first one have some information about file
>         format,
>         > which make our convert tool works correctly, and which the
>         second one
>         > doesnt have.
>         >
>         > Can you explain to me this different, and how can i get the
>         information
>         > as the first one?
>         >
>         > Thanks in advances,
>         > Quyps
>         
>         This question have been asked for a while, I really need some
>         help
>         here?
>         
>         Thanks in advance.
>         Quyps
>         
>         
>         --
>
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> 
> 
> -- 
> Steve Murphy
> ParseTree Corp
> 
> -- 
> _____________________________________________________________________
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